Gypsum wood fiber articles and methods of making same
View Patent ↗Emulsions are provided which are useful in imparting water-resistance to gypsum wood fiber products. In one embodiment, the emulsions comprise a wax or a combination of waxes, an alkyl phenol, at least one surfactant, Polynaphthalenesulfonic acid, and an alkali metal hydroxide. In another embodiment, the emulsions comprise a wax or a combination of waxes, an alkyl phenol, at least one surfactant, polynaphthalenesulfonic acid, an alkali metal hydroxide, and a complexed starch.
1. A gypsum wood fiber article comprising:
(a) a wood fiber;
(b) gypsum; and
(c) a dried an emulsion comprising:
at least one wax;
a C 24 -C 36 polymerized methylene coupled alkyl phenol;
at least one surfactant;
polynaphthalenesulfonic acid;
an alkali metal hydroxide; and
water.
2. The gypsum wood fiber article of claim 1 , wherein the C 24 -C 36 polymerized methylene coupled alkyl phenol is present in an amount from about 0.5 to about 10 wt. %, based on total weight of the emulsion.
3. The gypsum wood fiber article of claim 1 , wherein the surfactant is selected from the group consisting of a sorbitan ester, a polyoxyethylene sorbitan ester, and combinations thereof.
4. The gypsum wood fiber article of claim 3 , wherein the surfactant is present in an amount from about 0.5 to about 5 wt. %, based on the total weight of the emulsion.
5. The gypsum wood fiber article of claim 1 , wherein the at least one wax comprises a first wax having a melting point of at least 120° F., and a second wax that is a saponifiable wax.
6. The gypsum wood fiber article of claim 5 wherein the first wax is present in an amount from about 30 to about 45 wt. % and the second wax is present in an amount from about 3 to about 5 wt. %, based on the total weight of the emulsion.
7. The gypsum wood fiber article of claim 1 , wherein the polynaphthalenesulfonic acid is present in an amount from about 0.25 to about 5 wt. %, based on the total weight of the emulsion.
8. The gypsum wood fiber article of claim 1 , wherein the emulsion further comprises a starch.
9. The gypsum wood fiber article of claim 8 , wherein the starch is a complexed starch comprising a complexing agent selected from the group consisting of a borate compound and a molybdenum compound.
10. The gypsum wood article of claim 1 , wherein the gypsum wood article is a wall board or a sheathing.
11. The gypsum wood fiber article of claim 1 , wherein the wood fiber is selected from hardwood and softwood sources, and mixtures thereof.
12. The gypsum wood fiber article of claim 1 , wherein
the at least one wax comprises a first wax having a melting point of at least 120° F. in an amount of about 30% to about 45% by weight, based on the total weight of the emulsion; and a saponifiable wax in an amount from about 3% to about 5% by weight, based on the total weight of the emulsion;
the at least one surfactant comprises a combination of surfactants in an amount from about of about 0.5% to about 5% by weight, based on the total weight of the emulsion;
the C 24 -C 36 polymerized methylene coupled alkyl phenol is present in an amount from about 0.5% to about 10% by weight, based on the total weight of the emulsion;
the polynaphthalenesulfonic acid is present in an amount from about 0.25% to about 5% by weight, based on the total weight of the emulsion;
the water is present in an amount from about 45% to about 65% by weight, based on the total weight of the emulsion; and
the alkali metal hydroxide is present in an amount from about 0.5% to about 3% by 15 weight, based on the total weight of the emulsion.
13. A method of making a gypsum wood fiber article of claim 1 comprising the steps of:
(a) mixing a slurry comprising a wood fiber; gypsum; and an emulsion comprising, the emulsion comprising at least one wax, a C 24 -C 36 polymerized methylene coupled alkyl phenol, at least one surfactant, polynaphthalenesulfonic acid, an alkali metal hydroxide; and water;
(b) distributing the slurry onto a vacuum wire for formation of a mat;
(c) partially drying the mat of step (b);
(d) compressing the mat of step (c) through a series of vacuum belt rolls; and
(e) drying the compressed mat of step (d) in an oven.
14. The method of making a gypsum wood article of claim 13 , wherein the slurry comprises,
(i) from about 5 wt. % to about 50 wt. %, based on the total weight of the slurry, of a wood fiber,
(ii) from about 5 wt. % to about 50 wt. %%, based on the total weight of the slurry, of gypsum, and
(iii) from about 1 wt. % to about 3 wt. %, based on the total weight of the slurry, of the emulsion.
15. The method of making a gypsum wood article of claim 13 , wherein the gypsum wood article is a wall board or a sheathing.
16. The method of making a gypsum wood article of claim 13 , wherein the wood fiber is selected from hardwood and softwood sources, and mixtures thereof.